Value of FDG PET/CT in indeterminate infiltrative hepatic tumors in an endemic area of viral hepatitis

Objectives Infiltrative hepatic tumors in conventional imaging modalities are a continuing diagnostic challenge in clinical practice, especially in an endemic area of viral hepatitis. This study aims to assess the effectiveness of FDG PET/CT in indeterminate infiltrative hepatic lesions seen on CT or MRI.

Methods Dual-phase PET/CT scans were performed in 32 patients. Variables analyzed included visual scores (VS), SUVmax, and ratios of tumor to non-tumor SUVmax (TNR). Final diagnosis was histopathology or clinical follow-up.

Results Malignancy was proven in 27 patients: cholangiocarcinoma (CC) in 22 and hepatocellular carcinoma (HCC) in 5. 5 subjects had benign strictures. There were 25 patients with FDG-avid hepatic tumors. Sensitivity, specificity, PPV, NPV, and overall diagnostic accuracy using VS were 85%, 60%, 92%, 42%, and 81%. SUVmax and TNR values were significantly higher in infiltrative malignancies than benign strictures, and in CCs than HCCs. Furthermore, VS obtained from early-phase scans were as efficient as SUVmax and TNR from dual-phase imaging. PET/CT detected unexpected distant metastases with high sensitivity 92% and PPV 82%. 11 patients (34%) have clinical treatment plans altered by PET/CT alone.

Conclusions FDG PET/CT provides high accuracy in diagnosing indeterminate infiltrative hepatic tumors on CT or MRI, and offers an incremental value regarding unsuspected occult metastases. Infiltrative CC can be differentiated effectively from HCC and benign strictures. In addition, VS offers similar diagnostic value as the dual-phase protocol.